草田轮作系统中不同施氮梯度下玉米产量和土壤N2O气体排放特征OA

Nitrogen is an essential nutrient in the crop growing period.Applying an alfalfa and grain crop rotation can reduce the N fertilizer input in the subsequent crop.The impact of a reduction in nitrogen(N)fertilizer use on the yield,agronomic traits,N-use efficiency,and N2O gas emissions of subsequent grain crops in arid regions is unclear.Field experiments were conducted by planting maize after the alfalfa growing period.A completely randomized design was used for three nitrogen application levels:N1(maize was planted with a conventional nitrogen level,180 kg·ha-1),N2(maize was planted with a 30%decrease in the conventional N level),and N3(maize was planted with a 50%decrease in the conventional N level).A maize monoculture system(N0,maize monoculture at a conventional N level)was set as the control.The dry matter yield of maize decreased,and the grain yield increased initially and then decreased with the decrease in the N application.In the forage-grain rotation system,the N-use efficiency and N-partial productivity of maize increased when the N application decreased.The different N application levels had no marked effect on the dry matter and grain yields of maize planted after alfalfa,with an average of 24.3 and 12.3 t·ha-1 among treatments,respectively.Compared to the N0 treatment,the N-use efficiency and N-partial productivity of maize increased by 155.9%and 131.9%,respectively,in the N3 treatment(P<0.05).In the forage-grain rotation system,cumulative soil N2O emissions showed an initial increase followed by a decrease with reducing nitrogen application rates.In N2,the cumulative soil N2O gas emissions increased by 4.7%compared to the N0 treatment(P<0.05).Planting maize after the alfalfa growing period in the arid region of Ningxia can effectively utilize the nitrogen fixation ability of this leguminous crop.Reducing N applications by 50%for subsequent grain crop will not only decrease production costs and N2O gas emissions,but will also improve N-use efficiency and N-partial productivity,which is of great importance in ensuring stable grain production and promoting ecological safety in the southern mountainous areas of Ningxia.